This is an amazing find....an incredible stoneware Rum jug found in Soncy Bay. The jug was almost completely buried in the hard sand at about 65' deep, I had been fanning quite a large hole  when I started finding lots of broken pottery and the black glass bottle...the jug wasn't immediately recognizable as the exposed top had lots of leafy growth on it...as I started uncovering the rest of the body I thought that it must be broken, but as I fanned the rest of the sand away I was excited to see that it was completely intact. 
A friend who has a website about - 19th Century Bottles of the British Military - says SRD stands for Supply Reserve Depot and these jugs were used during WW l to supply the troops on the front lines with daily rations of Rum. Other names for the initials among soldiers were: Seldom Reaches Destination and Soon Runs Dry.